Apparatus for straightening metal by stretching

ABSTRACT

In an apparatus for straightening a continuously running metal strip with a stretching operation, there provided a hold-back roll assembly and a drawing roll assembly; every roll in both roll assemblies has the same diameter and is, with the exception of the fastest roll in one assembly and the slowest roll in the other assembly, associated with a separate differential gearing, the output rpm of which is individually variable by a regulating device in accordance with the required rpm increase or rpm decrease of the associated roll with respect to the adjacent roll.

United States Patent [1 1 Miinchbach Jan. 3, 1974 [54] APPARATUS FORSTRAIGHTENING 3,641,797 2 1972 Bell et al 72 205 x METAL BY STRETCHING3,580,033 5/1971 Gay 72/205 3,427,848 2/1969 Gay 72/205 Inventor: CurtMunchbach, 3,377,830 4/1968 Campbell... 72/205 Pforzheim-Sonnenberg,Germany 3,362,202 1/1968 Gay 72/160 [73] Asslgnee' a 'i PrimaryExaminer-Milton S. Mehr P orzheim-Brotzingen, Germany Att0rney Edwin E.gg [22] Filed: Mar. 31, 1972 211 App]; No.: 240,135 [57] ABSTRAQCT In anapparatus for straightening a contznuously run- 1 ning metal strip witha stretching operation, there prol Foreign Applicatiofl Priority Datavided a hold-back roll assembly and a drawing roll as- Apr. 14, 1971Germany ..P 21 18 051.8 sembly; every roll in both roll assemblies hasthe same diameter and is, with the exception of the fastest roll [52]U.S. Cl. 72/160, 72/205 in one assembly and the slowest roll in theother as- [5] B2ld 1/02, B2lb 39/08 sembly, associated with a separatedifferential gearing, [58] Field of Search 72/205, 160, 249 the outputrpm of which is individually variable by a regulating device inaccordance with the required rpm [56] References Cited increase or rpmdecrease of the associated roll with UNITED STATES PATENTS respect tothe adjacent roll. 3,626,737 12/1971 Defontenay 72/205 4 Claims, 5Drawing Figures PMENIED JAN 8574 SHEET 2 OF 5 Fig. 2

II I SHEET 3 OF 5 PATENTED 8 5974 SHEET l 0F 5 Fg. z

II II APPARATUS FOR STRAIGHTENING METAL BY STRETCHING BACKGROUND OF THEINVENTION This invention relates to an apparatus for straightening acontinuously advanced metal article, such as a metal strip, by astretching operation. The apparatus is of the type that has a hold-backassembly formed of rolls in an S-arrangement, a device for setting thedegree of stretch, and a drawing assembly formed of rolls in anS-arrangement. All the rolls have the same diameter and are rotatable bya common drive motor. The required step-down or step-up in theperipheral velocities of the different rolls is effected by differentialgearings.

In known straightening apparatus of the aforenoted type a differentialgearing is provided for every two rolls. The drive means is coupled tothe differential housing. In this manner, in case of different rpms ofthe rolls, a compensation is effected by means of the compensating bevelgear of the differential gearing. A buildup of the tension from one rollto the other may occur only if the differential gearing is connecteddirectly with one roll and through an intermediate ratio changing devicewith the other roll. The ratio changing device increases the directtransmission ratio of 1:1 by the value e to be discussed later. In casethis value which expresses the possible tension increment factor fromone roll to the other as a function of the looping angle and friction isexceeded, slippage will occur not only at that roll where such excessprevails, but also at the adjacent roll which is connected by means ofthe differential gearing. It is difficult to adapt such stretch-typestraightening apparatuses to the operational requirements, since noprovisions are made to adjust the individual drives. Furthermore,stretch-type straightening apparatuses of the aforenoted kind are verypoorly adapted, if at all, for treating very thin metal strips becauseof the effect of frictional losses in the drive gear assembly.

OBJECT, SUMMARY AND ADVANTAGES OF THE INVENTION It is an object oftheinvention to provide an improved stretch-type straightening apparatuswherein the driving means for the S-rolls may be adapted rapidly and ina simple manner to the operational requirements while it remainsunaffected by the efficiency of the drive gear assembly.

Briefly stated, according to the invention,in both the hold-back rollassembly and the drawing roll assembly, with each roll, with theexception of the roll driven with the highest or lowest speed in eachroll assembly, there is associated a differential gearing, whose outputrpm at the compensating gear carrier is variable by means of aregulating device in accordance with the required rpm increase ordecrease with respect to the adjacent roll. 1

By making possible an rpm regulation of each roll, its rpm may beadapted to the modulus of elasticity of the material to be treated.Furthermore, in the determination of the roll rpm it is possible to takeinto account the adhesion effect of the strip surface, the frictionalvalue of the individual rolls, as well as the change in the frictionalvalues. The latter may occur due to the soiling of the rolls, thepresence of oil or grease smudges, roll wear and regrinding.

It is a further advantage of the invention that the frictional losses inthe drive gear assembly. dependent upon operational conditions (such asstarting or braking), load conditions, the advancing speed of thematerial or the room temperature, do not eflect the accu racy of the setmagnitudes transmitted from the drive gear assembly to the rolls. Theaforenoted losses burden solely the motor which operates the drive gearassembly and have no effect on the value of strip adhesion of theindividual rolls. By means of automatic (or manual) readjustment of theregulating device, the lowering of the frictional adhesion values causedat high strip speeds by air inclusion and centrifugal forces may becompensated.

The invention will be better understood as well as further objects andadvantages become more apparent from the ensuing detailed specificationof several exemplary embodiments taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view of anS-type roll assembly formed of three rolls;

FIG. 2 is a block diagram illustrating schematically the stretch-typestraightening apparatus according to the invention and FIGS. 3, 4 and 5are block diagrams of modified arrangements of the drive gear assembliesaccording to the invention.

DESCRIPTION OF THE EMBODIMENTS Turning now to FIG.1, a metal strip istrained in an S-configuration about parallel supported rolls 1, 2 and 3.Rolls 1 and 3 are at the same height whereas roll 2 is displacedtherebelow.

The metal strip running onto the roll .1 from a reel (not shown) underan initial pull 8, engages the roll 1 through a looping angle a Inaccordance with the formula wherein e is the base of the naturallogarithm,

p. is the value of friction between roll and strip face,

a is the looping angle and S and S are the strip tensions upstream anddownstream of the roll 1, respectively,

S increases with respect to S as a function of the frictional value p.and the looping angle 01,. The strip runs onto the roll 2 under atension S which equals S but which, because of the looping angle a, andthe frictional value at the roll 2, increases to S as the strip runs offthe roll 2. The tension of the strip increases in this manner from rollto roll until a strip tension 8,, is reached.

According to the formula wherein S is the strip tension between tworolls,

1 is the length of the free strip portion between two rolls,

A is the length increase of the strip between two rolls,

F is the sectional area of the strip and E is the modulus of elasticityof the strip material, the

, strip exposed to the pulling force S S undergoes along the length 1between the run-off point of the roll 1 and the run-up point of roll 2an elastic elongation A, which is a function of the modulus ofelasticity E of the material and the pulling force S This elongation x,must be taken up slip-free by the roll 2 which is achieved by increasingthe peripheral velocity thereof.

Since the stip tensions S 5,, etc. have to increase up to the value ofthe stretching pull S the elongations for strips of different crosssection F are different between the individual rolls at structurallygiven fixed looping angles. Therefore, in a stretch-type straighteningapparatus the circumferential velocities of the invididual rolls in thehold-back assembly have to increase from roll to roll, while they haveto decrease in the drawing assembly. This change in the circumferentialvelocity of the rolls may be achieved either by providing rolls ofdifferent diameters in which case the rpms are identical or, if the rolldiameters are the same, then the rpm s have to be different.

In FIG. 2 there is schematically shown a drive gear assembly with theaid of which the different peripheral velocities of the rolls may beset, while each roll diameter has the same value. The drive gearassembly according to this exemplary embodiment serves a hold-backassembly and a drawing assembly formed of four rolls each.

In the embodiment illustrated in FIG. 2, the holdback assembly has fourrolls 16, 17, 18 and 19 and the drawing assembly has four rolls 20, 21,22 and 23. All these rolls are engaged by a running strip (not shown) ina manner similar to that illustrated in the three-roll S-assemblydescribed with reference to FIG.1. As seen, in the hold-back rollassembly rolls 16, 19 are the outermost rolls, while rolls 17, 18 areintermediate rolls, whereas in the drawing roll assembly rolls 20, 23are the outermost rolls, while rolls 21, 22 are intermediate rolls. Itis further apparent that the material, when the entire straighteningapparatus is considered, runs onto roll 16 and runs off roll 23.

For the driving of all the rolls there is provided a drive motor 24which rotates a main drive shaft 25 of the hold-back assembly. The shaft25 drives a stretch setting device 26 having an output shaft 27 whichconstitutes the main drive shaft for the drawing assembly. Since thedrive gear assembly associated with the drawing assembly is identical instructure and operation to that of the hold-back assembly, in thedescription that follows only the drive gear assembly of the latter willbe set forth in detail.

The main drive shaft 25 rotates the first roll 16 through a miter gear28 and a drive shaft 29. As it has been explained in connection withFIGJ, the first roll 16 of the hold-back assembly turns with thesmallest rpm with respect to the other rolls 17-19. Each roll 17, 18, 19rotates somewhat faster than the preceding roll in the hold-backassembly; for this purpose, each roll 17, 18, 19 is connected with themain drive shaft 25 through a separate gear assembly 40 which has twoinput shafts 31 and 35 driven through miter gears 30 and 34 by the maindrive shaft 25. It is noted that since each gear assembly 40 in thehold-back assembly is of identical structure and function, only thatassociated with roll 17 is described in detail. Thus, the output shaft33 extending from the gear assembly 40 is connected with the roll 17.

The gear assembly 40 includes a differential gearing 32 which is drivenby the input shaft 31 and which has an output shaft that constitutes theoutput shaft 33 of the gear assembly 40. The input shaft 35 isassociated with a steplessly adjustable non-slip gear ratio regulatingdevice 36 (for example, a P.I.V. drive), which, in turn, is connectedwith the compensating gear carrier of the differential gearing 32through an intermediate shaft 37, a step-down gear 38 and a furtherintermediate shaft 39. The rotational direction of the intermediateshaft 39 is so selected that the rpm of the output shaft 33 is increasedwith respect to the input shaft 31 to correspond to the required rpmincrease of the roll 17 with respect to the roll 16.

By virtue of the gear assembly 40 the roll 17 has a somewhat higherperipheral velocity than that of the roll 16 for taking up theafore-explained strip elongation A The extent of the rpm increase whichdepends on factors discussed earlier, is automatically or manuallyregulated in a stepless manner with the regulating device 36. With acorrespondingly large control range of the regulating devices 36 anydesired roll rpm may be set in the other gear assemblies 40.

By means of the stretch setting device 26, the rpm of the main driveshaft 25 transmitted to the hold-back assembly is transformed, as afunction of the extent of pull, into a higher rpm for the main driveshaft 27 and is thus transmitted to each gear assembly 40 of the drawingassembly.

Since by selecting the direction of rotation of the gear train 36, 38operating in shunt, the rpm of the output shaft 33 is increased ordecreased with respect to the rpm of the input shaft 31, variousarrangements of drive gear assemblies are possible which are illustratedin FIGS. 3, 4 and 5. Each gear assembly, however, has to be designed insuch a manner that in each case the first roll 16 in the hold-backassembly and the last roll 23 in the drawing assembly have the smallestrpm within their respective roll assembly.

In FIG. 3 in each roll assembly (that is, the hold-back roll assembly16-19 and the drawing roll assembly 20-23), the rolls having the highestrpm, that is rolls 19 and 20, are directly driven by the main driveshafts 25 and 27,whereas the adjoining rolls of decreasing rpms aredriven by the gear assemblies 40.

In the arrangement according to FIG. 4, the holdback assemblycorresponds to the arrangement according to FIG. 2 and the drawingassembly corresponds to the arrangement according to FIG. 3. Thus, theindividual gear assemblies 40 of the hold-back assembly transmit anincreasing rpm in the direction of the roll 19, whereas the individualgear assemblies 40 of the drawing assembly operate with decreasing rpms.

In the driving arrangement shown in FIG. 5 the holdback assemblycorresponds to the arrangement according to FIG. 3 and the drawingassembly corresponds to the arrangement according to FIG. 2. Thus, inthe holdback assembly the roll 19 is driven directly, whereas thepreceding rolls are driven with gradually decreasing rpms. In thedrawing assembly the roll with the lowest rpm (that is, roll 23) isdirectly driven by the main shaft whereas the preceding rolls are drivenby means of the individual gear assemblies 40 with increasing rpmsstarting with roll 22 down to roll 20.

The drive motor 24, as it can be observed from FIGS. 2-5, is associatedin each case with the miter gear of the hold-back assembly from whichthe driving of the corresponding roll is effected in a direct manner.

In view of the fact that the regulating devices 36, as it has been notedearlier, operate in a shunted manner, and further, since the output rpmof each regulating device is significantly decreased by an associatedstepdown gear, the effect on the roll of any possible rpm error in itsregulating device is reduced to a negligible value. This is so, becausethe roll rpm increments generated by driving the compensating gearcarrier of the differential gearing, are in the range of a fewthousandths of the rpm of the roll.

I claim:

1. In a stretch-type straightening apparatus of the known type that has(a) a hold-back roll assembly formed of a plurality of rolls in anS-arrangement, two of the rolls in the hold-back roll assembly beingoutermost rolls and the remainder being intermediate rolls, (b) meansfor driving each roll in said hold-back roll assembly with an rpm thatis greater than the rpm of any of the upstream rolls in the hold-backroll assembly, (c) a drawing roll assembly formed of a plurality ofrolls in an S-arrangement, two of the rolls in the drawing roll assemblybeing outermost rolls and the remainder being intermediate rolls, allthe rolls in both for driving each roll in said drawing roll assemblywith an rpm that is smaller than the rpm of any of the upstream rolls insaid drawing roll assembly, (e) a stretchsetting device determining theextent of material tension between the two roll assemblies and (f) acommon drive motor for rotating all the rolls, the improvementcomprising A. a separate differential gearing connected to everyintermediate roll and to one of the outermost rolls in both rollassemblies, each differential gearing having a compensating gear carrierand B. a separate regulating device connected at least indirectly to thecompensating gear carrier of each differential gearing for providing anrpm of the associated roll that is different from the rpm of any otherroll in the same roll assembly.

2. An improvement as defined in claim 1, including a main drive shaftrotated by said common drive motor and connected to each said regulatingdevice and to each said differential gearing.

3. An improvement as defined in claim 2, including means for steplesslyadjusting each regulating device.

4. An improvement as defined in claim 1, including a step-down gearingconnected between each regulating device and its associated differentialgearing.

1. In a stretch-type straightening apparatus of the known type that has(a) a hold-back roll assembly formed of a plurality of rolls in anS-arrangement, two of the rolls in the hold-back roll assembly beingoutermost rolls and the remainder being intermediate rolls, (b) meansfor driving each roll in said holdback roll assembly with an rpm that isgreater than the rpm of any of the upstream rolls in the hold-back rollassembly, (c) a drawing roll assembly formed of a plurality of rolls inan Sarrangement, two of the rolls in the drawing roll assembly beingoutermost rolls and the remainder being intermediate rolls, all therolls in both roll assemblies having the same diameter, (d) means fordriving each roll in said drawing roll assembly with an rpm that issmaller than the rpm of any of the upstream rolls in said drawing rollassembly, (e) a stretch-setting dEvice determining the extent ofmaterial tension between the two roll assemblies and (f) a common drivemotor for rotating all the rolls, the improvement comprising A. aseparate differential gearing connected to every intermediate roll andto one of the outermost rolls in both roll assemblies, each differentialgearing having a compensating gear carrier and B. a separate regulatingdevice connected at least indirectly to the compensating gear carrier ofeach differential gearing for providing an rpm of the associated rollthat is different from the rpm of any other roll in the same rollassembly.
 2. An improvement as defined in claim 1, including a maindrive shaft rotated by said common drive motor and connected to eachsaid regulating device and to each said differential gearing.
 3. Animprovement as defined in claim 2, including means for steplesslyadjusting each regulating device.
 4. An improvement as defined in claim1, including a step-down gearing connected between each regulatingdevice and its associated differential gearing.